avcodec/libopenh264enc: fix class_name

Reverts some accidental change in commit e621b1ca.
Reviewed-by: Jan Ekström <jeebjp@gmail.com>
Signed-off-by: Tobias Rapp <t.rapp@noa-archive.com>

libavcodec/libopenh264enc.c

@@ -75,7 +75,7 @@ static const AVOption options[] = {
 };
 
 static const AVClass class = {
-    .class_name = "libvo_amrwbenc",
+    .class_name = "libopenh264enc",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,